As with other animals, it is necessary to worm chickens regularly to prevent many health problems.
If you manage their house and run correctly, changing bedding and cleaning / providing fresh pasture for them this will help however even free range birds will need worming.

Worms cause damage to the digestive system of your birds which can sometimes lead to death. Products that are used to treat worms are not cheap but are necessary to prevent sick birds with increased food consumption, and fewer eggs.

Here is what you can do to help them:

Keep them clean and do not feed corn / scratch feeds in the litter if there are droppings in it.

Rest land periodically if you can to prevent a build up of worms.

Keep grass short, this allows the UV from sunlight to kill worm eggs (as well as preventing sour crop).

Use Apple Cider Vinegar regularly to lower the pH level in the stomach, making the gut slightly acidic, helping digestion and making it less friendly for worms.

Wormers / products that are used:

The only wormer tested and approved for use in chickens feed in the UK is Flubenvet .

Other Wormers that are sometimes prescribed by vets are Panacur and Ivermectin. These must be prescribed by your vet under what is called the 'cascade' as they are not licensed for chickens. Often there will be a withdrawal period for eggs as advised by your vet.

Verm-X is a product made from 100% natural ingredients. As a herbal product, this cannot be marketed as a wormer. There is controversy over the efficacy of Verm-X and any studies / trials performed by the manufacturer cannot be published. Some of the latest Verm-X packs are sold with a worm testing kit which is ultimately the best way to check to see if birds even need treating.

Diatom or Diatomaceous Earth / DE may help to prevent a build up of worms if fed to your birds. It also has many other uses like controlling red mites and lice so is very useful to have in stock.

Dosage information for these products should be available from your vet or on the product box / leaflet.

Remember if you treat birds once this may well kill all of the worms and eggs but you do need to have an ongoing treatment plan if there is a heavy worm load. Eggs that are picked up by the birds when feeding hatch later and a repeat treatment is required to continue to reduce the worm count.

The problem with Flubenvet (and probably other wormers) is that the dosage assumes you have several hens all of whom have the appetite for their food. What I and probably quite a few other folk need is information on just what the dosage is for one or two birds. Getting the dosage into the bird is not necessarily the problem, options are a paste on a small piece of bread or (my favourite) a crop feeding tube. (My crop feeding tube is a 10ml syringe with about 120mm of thin flexible plastic tubing)
Now with Flubenvet 1% powder I have made a best guesstimate of 1/8 teaspoon per day for a bird with what looks very like gapeworm.
While it is correct to say 'talk to your vet', this option is not always available on a Friday night or over the weekend , waiting till you can talk to your vet can for some folk mean a critical delay, (it has been reported to me that some folk have had to wait while their vet finds out and 'gets back to them ..later) In fairness I need to add I believe that many vets are increasingly clued up on poultry matter and most are as helpful as they can be.
So, could we have some suggestions for dosage rates for single birds with perhaps a guidance on what to allow for in terms of weight if this is critical? (May not be critical for most hens but could be relevant to various breeds of ducks..)
For example, is my guess at 1/8 teaspoon per day per battery type hen (for 7 days) in the right ball park? Can one overdose Flubenvet or other 'internal' wormers?

I have made some enquiries but unfortunately don't really have a satisfactory answer.

The problem is, the only information available from the manufacturer of Flubenvet is a certain quantity added to a certain weight of food. My guess (and it is a guess) is that a bird would normally eat a certain quantity of the medicated feed daily and the amount a chicken eats will depend on the size / weight of the bird - so roughly speaking, each bird is consuming the right amount depending on their size / weight.

So the only way to work this out would be to know how much feed your bird consumes on a typical day and calculate how much flubenvet would have been in that amount of food if it was medicated, then to take the same amount of Flubenvet and give it as you suggest. Personally, I would split it into 3 or 4 doses through the day so the bird doesn't have to cope with one big dose. Don't forget to continue this over the 7 day dosage period.

I don't know what would happen if the bird overdosed on Flubenvet, again, there is very little information to go on.

To elaborate on what I said: "it is necessary to worm chickens regularly" - I have had a number of people say to me over the years that they don't worm unless they think there is a problem since their birds are free range and less likely to get worms...

It is important to worm regularly (usually twice per year for Flubenvet, typically September and February) this is to keep the number of worms down within the digestive system. If the numbers build up to a sufficient level, they can impact (block) the digestive tract. When a wormer is used to kill them, they release a toxin and this can in fact kill the bird.

Free range birds are in fact more likely to get worms. Earth worms are the intermediate hosts - the eggs pass from chicken to the floor, get picked up by earth worms as they break things down in the soil and then transfered back to chickens when they eat the earth worms. Battery hens are in fact far less likely to be carrying as many worms.

My vet advised me to give a dosage of 1/4 scoop (scoop provided in the packet) of Flubenvet per 500g of food. He suggested I work out how much feed they eat over a 7 day period and premix the wormer with that. I worked it out that my 3 bantams consume about 1kg over 7 days (therefore 1/2 scoop in 1kg of hard feed). I mix it with 2 teaspoons of cod liver oil, to help it bind with the layers pellets. I read somewhere that normal size chickens should have a basic daily ration of 120g of layer's pellets or mash. Don't know if that helps at all... :P

Yes, the scoop will be a certain pre-determined weight of Flubenvet - so it is easier than weighing if you don't have accurate scales but here you have a certain quantity of Flubenvet added to a certain weight of food and are assuming the hen is eating her ration for the day.

The real difficulty is what if one of your chickens wasn't eating much because she was so impacted (blocked up) with worms... then you have to take a good guess at how much she eats in a day (120g is a good figure for a medium size hen) and dose her with the amount of flubenvet that would have been in 120g of feed for 7 days orally as chasingclouds suggests.

Here is a follow up to Chasing Clouds earlier post that was sent to me by PM:

chasingclouds wrote:Hi,Since posting last year about flubenvet using 1/8 teaspoon per bird have had some experience on how this works out in practice. You may recall I used a pelleting medium (aviary soft food/egg mix) with the 1/8 teaspoon to make two or three pellets and then put them down bird throat.

Firstly, I only lost one of the four birds that had gapeworm, the one that died was the one that showed symptoms first and because I didn't recognize the symptoms (nor did the person who sold them to me..) I started treating her too late. The other all showed signs of gaping but this quickly went away and a week after the end of dosing each of them with 1/8 teaspoon flubenvet, no more gapeworms could be seen in the droppings.

I then decided to try the Vermex process but found the hens would not touch the pellets, refused the drinking water so, being determined, I made up a crop feeding syringe tube to enable me to pop the stuff down their throats and I would know each one had been dosed (Once a month for three days using liquid Vermex). (Luckily I have the time to do this and the experience of crop feeding Budgies and Bourke's parakeets) This went on for some months then we decided to get some Columbines (nice birds but you need to keep calm with them!) and I decided that regardless of Vermex claims to deal with gape worm etc. that I would dose every one with pelleted flubenvet. I got half way through the dosage and suddenly found one of the older hens leaving a dropping at my feet. My wife didn't quite scream but said in a clear tone "Examine that NOW" I did and found a dropping stuffed full with round worm, several of which where over two inches long and one was just over 3inches long. These birds had been getting their Vermex because I had put it down each of their throats and marked them off on a list when I had done so, each bird has a unique ring on it so I knew I hadn't missed anyone.

So bottom line is 1/8 teaspoon seems to work well (using the 60g pot strength) and seems to chuck out those worms that Vermex don't clear out. I am informed it takes more than 4 weeks for a round worm to reach 3 inch leangth and the birds had been dosed two weeks before the flubenvet dosage of every one.

I personally feel quite safe in suggesting 1/8 teaspoon of flubenvet per hen - and many folk have small sets of measuring spoons in their kitchens. I reached my figure by various calculations on body weight and consumption weight but could not for the life of me do so again - I hate figures!

Sorry for the length, hope it helps, it may be helpful to post this figure somewhere for those folk who only have one or two hens and don't want to mix up 4kg of feed! Flubenvet may keep for 6 months but the mash won't!

A suggestion for those needing to make up layers mash with flubenvet for their (larger) flock. Start with the small measure of layers mash , add flubenvet then immediately add two or three handfulls of black niger seed, stir mix round then proceed with 'dilution' process of mixing this with increasingly larger amounts of layers mash. You can see broadly how well you are mixing the flubenvet by looking at how evenly the niger gets dispersed. Not infallible but gives you some idea how mixing is going.

Do feel free to quote any of this anywhere you feel it may be most useful